Control for fluid pressure devices



Patented June 21, 1938 A UNITED STATES z,12 1,ss`9

coN'raoL Foa Enom PRESSURE nEvIcEs George G.

Mummia Emile J. carleton,-

Holyoke, Mass.

ApplicationJune 13, 1936, Serial No. 85,008 s claims. (ci. sg-54) This invention relates to improvements in control devices for governing the application of iiuid under pressure to a power applying mechanism, such as a cylinder and piston or other motors of `the expansible chamber type.

The invention, while capable of general use, is especially suitable for use in connection with the operation of brakes and clutches. It is adapted for use with brakes and clutches of machinery performing heavy duty, such as cranes, hoists, power shovels, trucks, tractors, busses, locomo-v tives and the like. The invention is, however, equally capable of use with other classes of ma chinery not subjected to such heavy duty: and as conspicuous examples, the invention may be used to advantage to control the hydraulic brakes of an automobile or to control the winding drums of dipper trips, tag line winders, and hoisting and closing cables of clam shell buckets.

The invention has for an object'to provide a control device by means of which fluid pressure may be applied to the mechanism, as for example one or `more brakes, smoothly and gradually, from zero to a desired maximum by as small increments of pressure increase as may be desired and by means of which the pressure may be released in the same manner.

A further object of the invention is to provide a control device which may be set in any one of various positions to provide for the application of any desired degree of pressure on the power applying mechanisnband which will automatically maintain the pressure for which it is set,ad mitting or releasing uid 4tosaid mechanism as may be necessary to compensate for decreases or increases in pressure in such mechanism from4 whatever cause.

These andother objects will best be understood as the detailed description proceeds and they will be pointed out inthe appended claims.l

The invention will be disclosed with reference to the accompanying drawing in which:

Fig. 1 is a sectional elevational View of a control device embodying the invention,the parts being shown in the relative positions which theyoccupy when the brake is fully released;

Figs. 2, 3 and 4 are views generally similar to Fig. 1 but showing theparts in various other relative positions and illustrating, respectively, the iniiow of iiuid, the cutting off of fluid against inflow or outflow,` and the outflow of fluid; and

Fig. 5'is a diagrammatical view of a brakesystem, showing the relationship of the control device with other parts of the system.

Referring to this drawing, the control device includes a casing 6 aording a cylinder 1 which is entirely closedexcept for the ports 8, 9 and I0. Conveniently, the cylinder has a removable head II, held in place by screws I2 and forming one end of cylinder 1. -A control rodi I3 passes through head II and a suitable stuffing box I4, and is slidable therein in a direction axially of Y the cylinder 1, being movable back `and forth by any suitable means, manual or otherwise. The port 8 is formed in the opposite end of cylinder 1 and is adapted for connection to the motor means which is to be actuated by uid pressure. The ports 9 and I0 are for the inflow and outow respectively, of uid from the cylinder. Port 9 is formed in the peripheral wall of cylinder 1, at a point intermediate its ends, while port I0 is preierably :formed in head II.

Slidable in cylinder 1'is a piston I5 which may be, and preferably is, provided with rings I6 or other means to secure a liquid tight engage- 1 ment between the piston/and the cylinder wall. As shown, these rings are provided in sets, disposed one near each end of the piston. Between these sets of rings the piston is provided with an annular groove I1 of such length as to maintain communication with port 9 for every position that the piston may assume in cylinder 1. The piston has a coaxial bore 48,u forming a cylinder to slidably receive a piston valve I9, which is mounted on the inner end of the control rod I3 in such a manner th t the piston valve is free to seek its own bear ng in cylinder I8., This cylinder is closed at that end nearest port 8, and `at its other end is open and in free and constant communication with the right hand endA of cylinder 1 and thus with port I0. Cylinder, I8

opens-into a bore' 20 of slightly larger diameter which receives one end of a coil spring 2l, such end seating on the shoulder formed at the inter- `section of the bores I8 and 2li. 'Ihe other end of spring 2l is seated in a recess in head II. The N piston valve I9'has a passage 22 (Fig. l) extending coaxially from one end to the other, to equalize the pressure acting on opposite ends of the piston valve and to thereby balance the valve.\

This valve has an annular groove 23, which vis in constantl communication with groove Il and thus with admission port 9, by means of a radial tion of its axis. The piston 1 is provided with a passage 25 extending from the left hand end face of the piston longitudinally inward and terminating in a port 26 which opens into cylinder I8 and is adapted to be opened and closed by the piston valve I 9. The longer of the two cylindrical portions of large diameter of member I9 is effective for controlling port 26. Such portion may cover port 26 and entirely cut it oif from communication with both of ports 9 and I 0, as shown in Fig. 3; or it may be moved outwardly by a pull on rod I3 to admit iiuid from port 9 to passage 25 as shown in Fig. l2; or it may be moved inwardly by a push on rod I3 to connect passage 25 to port Il) as shown in Figs. 1 and 4.

The control device described may be used in various fluid pressure systems which include a motor means operable by iluid pressure. One exemplary apparatus, with which the control device may be used, is shown in conventional form in Fig. 5. 'This iigure shows an hydraulic brake apparatus, whereof the shoe and drum are shown at 30 and 3I, respectively. The shoe 30 is operatively connected to the piston rod 32 of a motor of the expansible chamber type, including a piston 33 and cylinder 34, the right hand end of which is connected by a pipe 35 to the port 8 of the control device. 'I'he left hand end of cylinder 34 is vented, as indicated, and is provided with a spring in chamber 36 for returning the piston 33 when the iluid pressure is released from the cylinder. The port 9 is connected by a pipe 3-1 to any suitable source of uid pressure. As shown herein, it is connected to a reservoir 38 which is supplied with liquid through a pipe 39 by a suitable pump, such as the gear pump 40. This pump draws liquid from a supply tank 4I through the suction pipe 42. A by-pass 43 is provided around the pump 40, interconnecting the suction and discharge pipes 42 and 39, and this by-pass is controlled by a relief valve 44, which opens when the pressure in pipe 42 reaches a predetermined value and allows liquid to pass back to the suction pipe 42. The arrangement aiords a supply of liquid at a constant predetermined pressure. The reservoir 38 is closed at its upper end and the pipe connections 31 and 39 both enter at the opposite end, whereby air is trapped in the upper portion oi' the tank, forming an air cushion indicated at 45, which functions to absorb shocks and provides for resiliency in the application of liquid pressure to the operating member 33. The port I is preferably connected as shown by a pipe 46 to the supply tank 4I and this tank is vented to the atmosphere, as indicated conventionally at 41. The pipe line 39 is preferably provided with one or more check valves 48 to prevent the return flow of liquid. If desired, the by-pass system 43, 44 may be omitted and the desired pressure in tank 38 secured by regulating the total amount of iluid in the system as a whole. This will not give as accurate regulation of pressure in the tank 38 as the construction iirst described, but is simpler and uses less power since the pump 46 turns idly unless there is liquid reaching it from the tank 4 I. The variation of pressure is not of importance since the device, as will appear below, will operate to maintain at the port 8 a pressure determined by the setting of the control valve and unailected by variations in the pressure at the entrance port 9 as long as the latter is above the valve for whichv the control valve is set.

. It will be appreciated that the apparatus schematically shown in Fig. is merely an illustrative example of onevof many uses of the invention. The pressure fluid may be liquid or gaseous and is desired. The control device, of course, may

be located at any convenient point and that point may be, and usually is, remote from the power applying mechanism and pressure reservoir.

The operation of the control device will next be described. With the power applying mechanism in released or inactive position, the parts of the control device are positioned as shown in Fig. 1. The piston I5 has been moved by spring 2| to the left hand end of cylinder 1 and the piston valve I9 is in position to cut off the supply of pressure uid to port 26 and such port is open to the right hand end of cylinder 1 and thus to port I 0, whichis in communication with the atmosphere through the pipe connection 46 with the vented tank 4I. To apply pressure to power applying mechanism, the control rod I3 is moved to the right, thus moving the piston valve I9 to cut oi the communication between ports 26 and I0 and open port 26 to the annular space 23. The condition which then exists is shown in Fig. 2, and fluid enters port 26 and passage 25 into the left hand end of cylinder 1 and by way of port 8 and pipe 35 to the power cylinder 34. As the pressure builds up in the left hand end of cylinder 1, the piston I5 is moved to the right, stressing spring 2|, and the piston continues to move until the force of the stressed spring is balanced by the pressure in the left handend of the cylinder. Assuming that the piston valve I9 is stationary, the movement of piston I5 will eventually cause port 26 to be covered by the valve and the supply of pressure iiuid to be cut off, as shown in Fig. 3. If valve I9 is now moved further to the right, port 26 will again be opened and iluid will enter the left hand end of the cylinder and move piston I5 to the right until the supply of pressure fluid is again cut oil. Each increment of movement of rod I3 to the right, results in the establishment of increased pressure in the left hand end of cylinder 1. Such pressure is proportional to the movement of the rod. A slow movement of the rod, or a movement of it step by step by small I increments, enables the pressure to be gradually built up from zero to the desired maximum and the increments of pressure increase may be as small as desired. In like manner the pressure may be released gradually by a slow movement oi' rod I3 to the left or by a movement of it step by step. If the rod I3 is moved inwardly a slight distance as shown in Fig. 4, valve I9 will uncover port 26 and allow it to communicate with the outflow port I0 and iiuid will leave the left hand end of cylinder 1. As the pressure at such end diminishes, the spring 2I will move piston I5 to the left until the port 26 is covered by valve I9. A less pressure then exists in the cylinder. By continued movement of rod I3 to the left, this pressure may be reduced until it reaches zero when the parts are again positioned as shown in Fig. 1.

Assuming now that the rod I3 has been moved to a certain position and is held stationary in such position to maintain a predetermined pressure on the power applying mechanism, the desired predetermined pressure will be automatically maintained. For example, suppose the valve I9 is held stationary in the position of Fig. 3,

now if there should be a leak in the power applying mechanism or in thepipe connections thereto, the pressure in the left hand end of cylinder I will drop and as soon as it does so, spring ZI moves piston I to the left,l allowing pressure iluid to be admitted to said end or the cylinder until the desired pressure is reestablished, when piston I5 will again be moved back -der 'I until the desired pressure is reestablished,

when piston I5 will again be moved back into the illustrated position. Y

In a similar manner the pressure at port 8 -will be unaffected by variations in the pressure at the port 9 due to variations in the pressure in the supply tank 38 as long as this pressure is greater than that desired at the port Il. The pressure from this reservoir is balanced both upon the piston I5 and upon the valve I 9, and the position of the piston is due solely to the balance between the fluid pressure at one end and the spring pressure at the other. 'I'his complete separation oi the output pressure from the input pressure (subject only to a minimum value of the latter) is of great importance in many installations.

The invention aii'ords an easily operable control because the valve I9 is balanced and it is thus feasible for the control to be used to govern the application 'ci very heavy pressures to` power applying mechanisms, such as the brakes or clutches of power shovels, cranes, holsts and all kinds of material handling machinery, also for large trucks, busses, tractors and the like. The control' device is not only easily operable but, more important still, it is sensitive and enables the pressure to be applied or diminished' smoothly, evenly and as gradually as desired, even after the iuid pressure device has reached a stationary condition. `It also provides for the maintenance of a selected pressure, irrespective of conditions which tend to diminish or increase the pressure in the power applying mechanism.

What we claim is:

1,. A control device for fluid-pressure devices, comprising a casing, a piston movable back and forth therein and subjected none side to and movable in one direction by t e p essure ofy the uid supplied to the'device, yielda le means acting on the other side of the piston for 'moving it in the opposite direction, a. single piston valve element mounted "in said-piston for movement` back and forth in a path parallel to that of the piston, and a control rod fixed directly to said element and extending outside said casing, said piston having apassage 'leading from the firstv named side to said valve element and controlled by the latter and having fluid admission and discharge passages. alternatively connectible to said rst named passage by said valve element.

2. A control device for uid pressure devices, comprising, an outer cylinder having at one end a port for connection to the device and near `the opposite end a port for the discharge of Huid and intermediate its ends a port for the adnnssion of fluid, a piston in said cylinder, a spring for moving the piston toward the iirst-l named port,'said piston having an inner cylinder open at one end for communication with said discharge port and closed at the opposite end, said piston having a passage for affording constant communication between said admission port and the closed end of the inner cylinder and a second passage between the inner cylinder and the rst ,named end. of the outer cylinder, a piston valve mounted in the inner cylinder and operable to closesaid second passage or to con- 'neet it to either end' of the inner cylinder, and

a control rod connected to the piston valve and extending outside the outer cylinder.

3. A control device for iluid pressure devices, comprising an outer cylinder having-at one end a port for connection to the device and near the opposite end a port for the discharge of uid and intermediate its ends a port for the admission of fluid, a'piston in said cylinder, a spring for moving the piston toward the iirst-named' port, said piston having anyinner cylinder open at one end for communication with said discharge port and closed at the opposite end, said .piston having a passage for affording constant comprising an outercylinder having at one end Y a port for connection to the device and near the opposite end aport ior the discharge of'uid and intermediate its ends a port for the admisjsion'of fluid,- a piston in said cylinder having intermediate its ends a recess in its periphery of suiiicient length to afford communication-with said admission port at all positions whichtne piston may assume throughout its range of movement, a sprir'g for moving the piston toward the mst-named port, said piston having an inner cylinder openfat oneend for communication with' said discharge port and closed at the opposite end, said piston having a passage connecting the inner cylinder `at a point intermediate its ends to said recess and a second pas-.- sage connecting the inner cylinder at a point between the rst passage and said open end to the iirst named end of the outer cylinder, a piston valve mounted in the inner cylinder and operable to close said second passage or to connect it to either end of the inner cylinder, and a control rod connected to the piston valve' and extending outside the outer cylinder.

5. A control device for a uid pressure device comprising a casing forming the sides and one end of a pressure chamber,A an output port opening from said chamber for connection to the device to be operated, a member movable in said casing and having one end wall acting as the second end of the. pressure chamber, a spring urging said member towards the iirst named end ofthe chamber, a single valve member within the casing and movable relative thereto and to 'said movable member, a control rod fixed dlrectly to said valve and extending outside the easing, a iluid pressure'port opening into the casing, afdischarge port opening into the casing. and passages in said movable member connecting with said pressure chamber, said ports,

rst named position and the movable member moves in a direction to compress the spring it will connect the pressure chamber with the passage in the movablefmember leading the exhaust port and block off connection of the pressure 5 chamber to the inlet port.

GEORGE G. MORIN. EMILE J. CARLETON. 

